European Pat. No. 32 244 describes a composite film or sheet, in which one layer is made from a material which is insoluble in water, but soluble in acid or basic aqueous media. The material is preferably a copolymer of an unsaturated organic carboxylic acid with a neutral monomer.
EP-OS 143 935 describes copolymers of acrylate and acrylic ormethacrylic acid insoluble in water, but soluble in a basic medium which can be used in may different ways and which have good mechanical characteristics.
The object of the present invention is to make available polymers, which are insoluble in a neutral and basic medium, but can be dissolved in acid, aqueous media.
The invention therefore relates to amino group-containing polymers of at least one acrylate of formula I ##STR1## in which R.sub.1 is hydrogen or methyl and R.sub.2 an alkyl radical with 1 to 18 C-atoms, and an amino acrylate of formula II ##STR2## in which R.sub.1 has the same meaning as hereinbefore and R.sub.3 is an alkyl radical with 1 to 6 C-atoms and R.sub.4 and R.sub.5 are the same or different and represent hydrogen or alkyl radicals with 1 to 4 C-atoms, as sell as optionally neutral vinyl monomers, which differ from the acrylates of formula I, and conventional polymer additives.
Polymers with the above composition represent a valuable supplement to the known polymers soluble in basic media and make available numerous new possible uses.
The radical R.sub.2 of the monomers of formula I is preferably an alkyl radical with 1 to 4 C-atoms. Typical representatives of monomers of formula I are methyl methacrylate, ethyl acrylate, butyl acrylate and butyl methacrylate. In the aminoacrylates of formula II, the radical R.sub.3 is preferably C2. The radicals R.sub.4 and R.sub.5 are preferably alkyl radicals, especially methyl or ethyl. A nitrogen atom can also be located within a ring provided in place of the radicals R.sub.4 and R.sub.5, e.g. in a morpholine ring. A particularly suitable representative of the amino acrylates is dimethylaminoethyl methacrylate.
The third monomer can be a monomer of the group of vinyl ethers with 3 to 18 C-atoms, particularly vinyl isobutyl ethers, aromatic vinyl hydrocarbons with 8 to 11 C-atoms, particularly styrene, acrylate or methacrylate with an alcohol radical with 1 to 18 C-atoms, particularly n-butyl acrylate, butyl methacrylate and stearyl methacrylate.
The molar ratio of the monomers of formula I to the monomers of formula II is preferably in the range 8:1 to 2:1, particularly 6:1 to 3:1. The ratio of the aminoacrylate to the terpolymer, provided that one is present, is preferably 1:0.1 to 1:1, particularly 1:0.2 to 1:0.3. The molecular weight of the polymers is preferably in the range 40,000 to 200,000 particularly 50,000 to 80,000.
For the production of the inventive polymers, the monomers are preferably polymerized directly in the form of the acrylate or aminoacrylate.
Polymerization can take place continuously and for this purpose use is made of special extruders, particularly installations with several series-connected extruders. The polymers can be in different states, e.g. in the form of solutions or dispersions, which are usable for adhesive joints or coatings, as well as powders. As a result of their thermoplastic characteristics, they can also be present in the form of shaped articles, particularly granules, films, deep drawn parts, injection moulded parts, pressed or blown parts and plates. These shaped articles can be provided with acid sensitive coatings, in order to make them water-soluble on the side provided with the coatings.